Sports boot shell with comfort sock

ABSTRACT

A sports boot shell of which at least a part of the wall is composed of a sock covered with a rigid material in plastics material, wherein the sock includes, on its inner surface, an insulating means limiting losses of heat by radiation, which may be a polyurethane coating that includes aluminum particles or aluminum pieces bonded on the inner surface. The process for manufacturing such a boot comprises the step of lasting the sock prior to injection-overmolding of plastics material in order to form the wall of the shell.

BACKGROUND OF THE INVENTION

The invention relates to a sports boot shell or sports boot shellsubassembly and also to the sports boot itself, and is particularlysuited to the field of boots for boards for gliding, such as skiing orsnowboarding, or skating boots, which are subjected to significantstresses during use and for which a particularly robust structure isrequired, although they must offer a high level of comfort, particularlyas regards warmth. The invention also relates to a process formanufacturing such a shell.

A ski boot is a good example of a sports boot that, on the one hand, hasto be very robust and, on the other, has to offer a high level ofcomfort. Indeed, such a boot is subject to numerous stresses during useand consequently has to be very strong. A high level of stiffness isalso required in order to achieve a good performance on the part of theboot, which, as intermediary between the skier and the ski, transmitsthe skier's effort to the ski in order to guide the latter. However, itsconstraints in terms of comfort are also significant. The boot must, inparticular, have sufficient flexibility to enable the skier to open itin order to put it on and to take it off, enable him to flex his kneesforward in order to ski, and provide him with sufficient comfort,particularly in terms of warmth, despite being used in extremetemperature conditions and in a wet, aggressive environment.

DESCRIPTION OF THE PRIOR ART

As a response to these significant, contradictory constraints, prior-artboots are composed of a stiff upper into which a liner is inserted. Thestiff upper is composed of a shell surrounding the foot and a collararticulated on this shell and surrounding the lower leg. This upper ismade from stiff material and is produced via a process of dualinjection-molding of two plastics materials of different stiffness, inwhich the quantity of each of these materials is stipulated for eachzone of the upper in order to satisfy the requirements for stiffness andcomfort. The role of the inner liner for accommodating the foot is toguarantee the skier's comfort.

Such conventional boots present the following drawbacks:

the upper is often too uncomfortable for the skier and the liners do notsufficiently offset this weakness in order to achieve a satisfactoryoverall level of comfort;

the upper requires complex liners in an attempt to obtain maximumcomfort;

the upper is unattractive.

Patent FR 1 565 339 describes a solution that is slightly different andconsists in providing a lining inside the shell and a manufacturingprocess based on the overmolding of a plastics material over this liningshaped in a mold. This solution is, however, insufficient to fulfill thecomfort and stiffness constraints.

Patent EP 1 172 042 describes a boot consisting of a flexible upper in atextile material in the form of a boot and of a shell injection-moldedin relatively stiff plastic, the upper and the shell being securedtogether by means of the injection-molding of a flexible plasticsmaterial between the flexible upper and the shell, via the bottom. Thissolution is, however, insufficient to fulfill the comfort and stiffnessconstraints.

There is therefore a need for another solution that attempts to fulfillthe stiffness and comfort constraints, particularly in terms of warmth,mentioned above.

SUMMARY OF THE INVENTION

An object of the present invention consists in proposing a sports bootthat does not present the drawbacks of the prior art.

More precisely, a first object of the present invention consists inproposing a sports boot that offers good comfort, particularly in termsof warmth, and presents satisfactory stiffness.

A second object of the invention consists in proposing a sports bootthat is esthetically attractive.

A third object of the present invention consists in proposing a sportsboot whose manufacturing process remains simple.

According to the concept of the invention, the sports boot is based onan upper whose comfort is improved by means of a wall comprising aninner comfort sock that has insulating thermal properties with regardsto thermal radiation.

More precisely, the invention is based on a sports boot shell of whichat least part of the wall is composed of a sock covered with a rigidlayer in a plastics material, wherein the sock includes, on its innersurface, an insulating means limiting losses of heat by radiation.

The insulating means may consist of pieces of aluminum sheet bonded tothe inner surface of the sock or of a polyurethane coating that includesparticles of material possessing properties of reflection of thermalradiation, these particles possibly being made from aluminum.

According to a further variant embodiment, the polyurethane coatingforms a first inner layer of the sock, which is covered by anintermediate foam layer insulating against conduction of heat, then by athird layer in a compatible material in order to allow overmolding of aplastics material.

The sock may occupy a wide surface surrounding the foot and be connectedto a part in flexible plastics materials forming at least one flap overthe instep, which may itself be linked to a very flexible part, inleather, plastics or fabric, in order to form at least one very flexibleflap.

Advantageously, the stiff plastics material then covers the sock and itslink with the flexible plastics material. A third plastics material mayalso cover the border zone between these two plastics materials.

The invention also relates to a sports boot, and is particularly adaptedfor a ski boot that includes a shell as described above.

The invention also relates to the process for manufacturing a sportsboot shell comprising the following steps:

production of a sock from a fabric having a property of thermalinsulation against radiation;

lasting of the sock obtained;

injection-overmolding of a plastics material over the entire surfaceoccupied by the sock.

This process may include a step of linking the sock having a notch witha first flexible plastics material in order to form at least one flapcovering the notch, then the injection-overmolding of the secondplastics material so as to cover this link between the sock and thefirst plastics material, then the injection-overmolding of a thirdplastics material over the linking zone between the first two plasticsmaterials.

DESCRIPTION OF THE DRAWINGS

These objects, characteristics and advantages of the present inventionwill be set forth in detail in the following description of a particularembodiment given by way of non-limiting example in connection with theattached figures, in which:

FIG. 1 shows a perspective view of a ski boot shell according to oneembodiment of the invention;

FIG. 2 diagrammatically shows what would be a sectional view on II-II ofthe shell of FIG. 1, in which the thicknesses of the various layers aredeliberately exaggerated and the shapes simplified for reasons ofclarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a very sophisticated embodiment of theinvention applied to a ski boot shell. This shell is composed of threeplastics materials 1, 2, 3 obtained by means of three injection-moldingoperations. The zone in plastics material 1 is relatively flexible andconnected to more flexible parts 4, in leather, plastics or fabric, bymeans of stitching 5 in order to form two flexible flaps in the zonecorresponding to the instep and extending as far as the lower leg inorder to make it easier to put the boot on. The other end of these partsin plastics material 1 is connected by stitching 6 to an inner sock 7that therefore has a notch at the level of the instep zone, as shown inFIG. 2.

The sock 7 occupies a wide surface around the foot and includes aluminumin order to form a wall having a property of reflecting thermalradiation, which has the effect of preventing cooling of the inner linerand, more particularly, of the foot placed in this liner, which is at ahigher temperature than the outside temperature, by heat radiation. Moreprecisely, use is made for this sock of an aluminizedpolyurethane-coated fabric, the coating being placed on the inner faceof the sock facing the liner, which has, by virtue of the presence ofaluminum particles, the sought-after thermal property, associated,furthermore, with a bi-directional elastic property by virtue of thepolyurethane coating, which is advantageous for lasting andmanufacturing the sock and the shell. This fabric also has an attractiveesthetic appearance, demonstrating and directly taking advantage of thetechnical effect used in the present invention.

A variant embodiment of this sock 7 (not shown) consists in providingthree superposed layers:

the inner layer will likewise be an aluminized polyurethane-coatedfabric;

an intermediate layer will include an insulating foam in order to limitlosses of heat by heat conduction while fulfilling a shock-absorbingfunction;

a layer of attaching material compatible with the injection-overmoldedplastics 2 in order to allow overmolding and good adhesion as will bedescribed below. The attaching material may be a woven or non-wovenfabric.

As a supplementary variant embodiment, metallic particles other thanaluminum, offering similar properties, may be used.

Lastly, a further manufacturing variant may consist in bonding pieces orcutouts of aluminum film onto the inner surface of the sock. In order toobtain the elasticity required for lasting of the sock, these pieces ofaluminum sheet will be smaller on those parts of the sock 7 that requiregreater elasticity because they undergo significant deformation duringlasting, corresponding to the lateral parts of the foot, for example,and strips of larger dimensions will be used for the other parts of thesock, such as the sole and the toe. A kind of mosaic of aluminum pieceswill thus be created on the inner surface of the sock, making itpossible to obtain an effect equivalent to that obtained by thepreceding variant embodiments. It should be noted that it is unnecessaryto cover the entire surface of the sock, but the effect obtained will beall the greater if a larger surface area of the foot is covered, moreparticularly if the surfaces that are most vulnerable to the cold arecovered.

Finally, the essential characteristic of the invention is that the sock7 should include, on its inner surface, an insulating means limitinglosses of heat by radiation.

The sock 7 as a whole is covered by a stiff plastics material 2 thatgives the shell its stiffness in its lower part. This zone in plasticsmaterial 2 therefore occupies a surface surrounding the foot around awide notch extending over the instep and rising as far as the lower leg.It also covers the stitching 6 between the flap and the sock 7 in orderto protect it and to guarantee its leaktightness. The plastics material2 is obtained by an injection-molding operation over the sock 7 and overthe stitching 6, which results in adhesion between the zone in material2 and the sock 7.

The material of the sock 7 is thus chosen to withstand the temperatureof the injection-molded plastics material.

Lastly, in the embodiment shown, zones in a third plastics material 3are obtained by means of a third injection-molding operation. Thismaterial 3 makes it possible to obtain esthetic effects in zones of theshell where only the material 2 is present and also attractive estheticeffects in other zones where the three different materials combine,while still making it possible to obtain different mechanical propertiesthrough the combination of plastics materials having differentproperties. Furthermore, this material 3 covers a large surface area ofthe linking zone 8 between the above two plastics materials 1 and 2,which improves the performance of this link in terms of longevity,leaktightness and strength. Indeed, this zone 8 comprises the axes ofrotation of the flaps formed by the plastics material 1 and the veryflexible part 4 relative to the stiffer shell in plastics material 2 andthus undergoes particular, repetitive stresses. Moreover, this zone 8also includes the stitching 6 between the sock 7 and the material 1,which is fragile by nature and not leaktight. For these reasons, thiszone is more vulnerable and justifies the superposition of the threeplastics materials 1, 2, 3 obtained by triple injection-molding.

In brief, a first solution for achieving the sought-after objectsconsists in providing a shell whose wall includes an inner sock havingproperties of insulation against losses of heat by radiation and anattractive esthetic appearance. A second, supplementary solutionconsists in providing flexible flaps based on flexible plastics,leather, fabric or any equivalent flexible material. A third solutionconsists in making provision for a triple injection-molding operation inorder to superpose three layers of plastics materials over certain zonesthat are particularly vulnerable.

The preceding, sophisticated embodiment described above with referenceto FIGS. 1 and 2 combines the three above solutions by way of example.

Nevertheless, other variant embodiments or combinations may beenvisaged. For example, one of the simplest solutions could consist in ashell composed of a sock comprising an aluminized polyurethane coatingcovered by a single plastics material, also forming the flaps, obtainedby a single plastics injection-molding step.

The invention also relates to the process for manufacturing such a skiboot shell, which comprises the following steps:

production of a sock 7 on the instep from a substantially elastic fabrichaving a property of thermal insulation against radiation;

lasting of the sock 7 obtained;

injection-overmolding of a plastics material 2 over the entire surfaceoccupied by the sock 7.

The first step may consist in using an aluminized polyurethane-coatedfabric, possibly a layer of insulating foam and an attaching fabric.

As a variant embodiment, the first step may consist in bonding pieces ofaluminum sheet on the inner surface of the sock.

As illustrated by the embodiment of FIGS. 1 and 2 described above, themanufacturing process may also comprise the following supplementarysteps:

before lasting of the sock 7, linking 6 between the sock 7 having a widenotch over the instep and an assembly 1, 4 in order to close the notchand to form at least one flap; more precisely, this step may include theproduction of a first stitching 5 between a part in plastics material 1formed by injection-molding and a flexible element 4 and a secondstitching between the part in plastics material 1 and the sock 7;

a last stage of injection-molding a third plastics material 3 over thetwo plastics materials 1 and 2 in their linking zone 8 may be effected.

Finally, the advantages of the solution are thus as follows:

the boot shell globally retains a conventional plastics materialstructure and thus has significant stiffness;

the shell has a wall insulating against losses by thermal radiation inorder to conserve the foot's heat, which increases its comfort;

the shell has an attractive esthetic appearance for its inner wall byvirtue of the material used for its radiation-reflecting properties, ofthe aluminum type, which also demonstrates implementation of theinvention;

according to a supplementary variant embodiment, the shell may compriseflexible flaps that make it much easier for the boot to be put on andtaken off, thereby further increasing its comfort;

according to a supplementary variant embodiment, the shell may comprisethe superposition of three layers of plastics material, obtained by atriple injection-molding process, in order to reinforce certain zonesthat would possibly be made fragile and to enhance the estheticappearance of the outer wall of the boot. It should be noted that thistriple injection-molding operation could, in fact, also be used in anyboot in order to take advantage of its primary function of mechanicalreinforcement of a more fragile zone and of its second function ofdecorating the outer surface of a boot;

the process for manufacturing such a shell remains simple, basedessentially on injection-molding steps as in the prior art;

this shell allows the use of liners that are not as warm and/or globallyless comfortable.

The embodiment described above relates to ski boots, but the concept ofthe invention could be reproduced for any other sports boot subject tosimilar constraints.

1. A sports boot shell of which at least part of the wall is composed ofa sock (7) covered with a rigid layer in a plastics material (2),wherein the sock (7) includes, on its inner surface, an insulating meanslimiting losses of heat by radiation.
 2. The sports boot shell asclaimed in claim 1, wherein the insulating means consists of pieces ofaluminum sheet bonded to the inner surface of the sock (7).
 3. Thesports boot shell as claimed in claim 1, wherein the insulating means isa polyurethane coating that includes particles of material possessingproperties of reflection of thermal radiation.
 4. The sports boot shellas claimed in claim 3, wherein the insulating means is a polyurethanecoating that includes aluminum particles.
 5. The sports boot shell asclaimed in claim 3, wherein the polyurethane coating forms a first innerlayer of the sock, which is covered by an intermediate foam layerinsulating against conduction of heat, then by a third layer in acompatible material in order to allow overmolding of a plastics material(2).
 6. The sports boot shell as claimed in claim 1, wherein the sock(7) occupies a wide surface surrounding the foot and is connected (6) toa part in flexible plastics material (1) forming at least one flap overthe instep.
 7. The sports boot shell as claimed in claim 6, wherein theplastics material (1) is linked (5) to a very flexible part (4) in orderto form at least one very flexible flap.
 8. The sports boot shell asclaimed in claim 6, wherein the plastics material (2) covers the sock(7) and its link (6) with the plastics material (1).
 9. The sports bootshell as claimed in claim 8, wherein a third plastics material (3)covers the border zone (8) between the two plastics materials (1, 2).10. A sports boot that includes a shell as claimed in claim
 1. 11. Aprocess for manufacturing a sports boot shell as claimed in claim 1,comprising the following steps: production of a sock (7) from a fabrichaving a property of thermal insulation against radiation; lasting ofthe sock (7) obtained; injection-overmolding of a plastics material (2)over the entire surface occupied by the sock (7).
 12. The process formanufacturing a boot shell as claimed in claim 11, wherein production ofthe sock (7) comprises a step consisting in bonding aluminum pieces ontoits inner surface.
 13. The process for manufacturing a boot shell asclaimed in claim 11, which also comprises the following step prior tolasting of the sock (7): linking (6) the sock (7) having a notch with aplastics material (1) in order to form at least one flap covering thenotch; and wherein injection-overmolding of the second plastics material(2) covers this link (6) between the sock (7) and the first plasticsmaterial (1).
 14. The process for manufacturing a boot shell as claimedin claim 13, which also comprises the supplementary step consisting ininjection-molding a third plastics material (3) over the linking zone(8) between the two first plastics materials (1, 2).
 15. The process formanufacturing a boot shell as claimed in claim 11, which also comprisesthe step of forming at least one flap via a link between the first orthe second plastics material (1; 2) and a very flexible part (4), inleather, plastics or fabric.